package org.shiro.filter;

import lombok.extern.slf4j.Slf4j;
import org.apache.shiro.web.filter.authc.BasicHttpAuthenticationFilter;
import org.shiro.token.JwtToken;
import org.springframework.http.HttpStatus;
import org.springframework.web.bind.annotation.RequestMethod;

import javax.servlet.ServletException;
import javax.servlet.ServletRequest;
import javax.servlet.ServletResponse;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;

/**
 * @author LENOVO
 */
@Slf4j
public class JwtFilter extends BasicHttpAuthenticationFilter {
  /** 判断用户是否想要登入。 检测header里面是否包含Authorization字段即可 */
  @Override
  protected boolean isLoginAttempt(ServletRequest request, ServletResponse response) {
    HttpServletRequest req = (HttpServletRequest) request;
    String authorization = req.getHeader("token");
    return authorization != null;
  }
/**执行登陆操作*/
  @Override
  protected boolean executeLogin(ServletRequest request, ServletResponse response)
      throws Exception {
    HttpServletRequest req = (HttpServletRequest) request;
    String authorization = req.getHeader("token");
    JwtToken token = new JwtToken(authorization);
    // 提交给realm进行登入，如果错误他会抛出异常并被捕获
    getSubject(request, response).login(token);
    // 如果没有抛出异常则代表登入成功，返回true
    return true;
  }

  /**
   * 这里详细说明下为什么最终返回的都是true，即允许访问 例如我们提供一个地址 GET /article 登入用户和游客看到的内容是不同的
   * 如果在这里返回了false，请求会被直接拦截，用户看不到任何东西 所以我们在这里返回true，Controller中可以通过 subject.isAuthenticated()
   * 来判断用户是否登入 如果有些资源只有登入用户才能访问，我们只需要在方法上面加上 @RequiresAuthentication 注解即可
   * 但是这样做有一个缺点，就是不能够对GET,POST等请求进行分别过滤鉴权(因为我们重写了官方的方法)，但实际上对应用影响不大
   */
  @Override
  protected boolean isAccessAllowed(
      ServletRequest request, ServletResponse response, Object mappedValue) {
    if (isLoginAttempt(request, response)) {
      try {
        executeLogin(request, response);
      } catch (Exception e) {
        System.out.println(e.getMessage());
        request.setAttribute("msg", e.getMessage());
        response401(request, response);
      }
    }
    // 如果请求头不存在 token，则可能是执行登陆操作或者是游客状态访问，无需检查 token，直接返回 true
    return true;
  }

  /** 对跨域提供支持 */
  @Override
  protected boolean preHandle(ServletRequest request, ServletResponse response) throws Exception {
    HttpServletRequest req = (HttpServletRequest) request;
    HttpServletResponse res = (HttpServletResponse) response;

    res.setHeader("Access-Control-Allow-Origin", req.getHeader("*"));
    res.setHeader("Access-Control-Allow-Methods", req.getMethod());
    res.setHeader("Access-Control-Allow-Headers", req.getHeader("Access-control-Request-Headers"));
    // 跨域时会首先发送一个option请求，这里我们给option请求直接返回正常状态
    if (req.getMethod().equals(RequestMethod.OPTIONS.name())) {
      res.setStatus(HttpStatus.OK.value());
      return false;
    }
    return super.preHandle(request, response);
  }
  /** 将非法请求跳转到 /401 */
  private void response401(ServletRequest request, ServletResponse response) {
    try {
      HttpServletRequest req = (HttpServletRequest) request;
      HttpServletResponse res = (HttpServletResponse) response;
      try {
        req.getRequestDispatcher("/401").forward(req, res);
      } catch (ServletException e) {
        e.printStackTrace();
      }
    } catch (IOException e) {
      e.printStackTrace();
      log.error(e.getMessage());
    }
  }
}
